Next year's Massachusetts Senate race, between Republican Sen. Scott Brown and Democratic Harvard professor Elizabeth Warren, is shaping up to be one of the most-expensive, most-watched races of the cycle. As we've noted previously, at least one recent poll gave Warren, the architect of the Consumer Financial Protection Bureau, a slight lead over Brown, who helped to gut some of the key provisions of last year's financial reform bill. Brown has $10 million in the bank; Warren raised $3 million in just her first six weeks as a candidate.

But for now, the race is something of a proxy war. Warren doesn't mention Scott Brown by name during her stump speech, choosing instead to cast her candidacy as a campaign against Washington inaction in the face of income inequality and crumbling infrastructure. Brown, for his part, has said he won't start campaigning until after New Year's. But in their absence, their surrogates are gearing up for a fight.

We've already flagged the new video from the Massachusetts GOP, which aims to turn Warren's support for Occupy Wall Street against her by framing her as the "Matriarch of Mayhem." The League of Conservation Voters, meanwhile, is pouring $2 million into a statewide ad buy tarring Brown as a shill for Big Oil and blasting Brown for receiving a zero-rating from the group, pointing to votes on environmental issues like the border fence:

Brown's Senate campaign responded with its own spot today, asking for supporters to fight back against "DC special interests," and helpfully noting that Brown "doesn't litter, he recycles":

Brown's response—that the construction border fence is clearly not an environmental issue—goes a long way toward explaining how he might have ended up with a zero-rating form the LCV. Anyway, it's worth noting that while the LCV has put a lot of money into its anti-Brown campaign—to the tune of $2 million—Brown's own video is online-only with no plans to air on television statewide. There will be a ton of outside money pouring into the race; this is just a preview.